1. Field of the Invention
This invention relates to water tight sealing between the concrete walls of septic tanks and like subterranean concrete vessels, and pipes which pass through the walls for carrying effluent therethrough. More specifically it relates to the design of a seal which is embedded in the concrete wall during casting of the concrete wall, that seals against any one of a variety of septic pipes that are used in the trade, including straight walled, corrugated, and schedule 40 pipe.
2. Description of the Prior Art
It is difficult to obtain a thorough, and long lasting seal between the concrete wall of a septic tank and a pipe that is inserted through the wall by way of the seal.
This is especially so when the pipe is of the heavy duty corrugated variety. The seal must permit a series of major and minor diameter ridges of the pipe pass through the seal without damage to the seal wiper when the pipe is installed in the septic tank, and seal thoroughly against the pipe at any place along the length of the pipe that the installer desires. The seal should not apply significant axial bias on the pipe which may cause it to shift after installation, because the person installing the system moves out of reach of the pipe after it is passed through the seal, and the seal should remain water tight even though the pipe may shift during refill of the septic system trench in which the septic pipe runs.
Many designs of cast in concrete seals for septic pipes have been developed in an attempt to solve the above problems.
U.S. Pat. No. 3,787,061 patented Jan. 22, 1974 by R. E. Yoakum describes a hollow walled ring of flexible elastomeric material, the hollow wall being trapezoidal in cross section. The radially outward facing wall of the ring has a pair of circumferential radially outward facing tangs. The ring is cast into the concrete wall peripheral to the opening through the wall to a depth in the wall to which the concrete encloses the tangs, the radially outward facing wall, and the front and back side walls of the ring.
The inner facing wall of the ring has a pair of extending, tapering, annular ribs which straddle the center of the inner facing wall and project obliquely from the inner facing wall, inwardly and toward the front and back opening of the seal.
The outer facing wall of the ring has a hole for inserting a one-coil spring from one end of the spring, into the hollow ring in order to snake it around within the hollow ring. After installation of the spring, the two ends of the spring extend from the hole and are accessible by the user by way of an axial passageway in the concrete adjacent to the outer facing wall.
The spring constricts upon the inner wall of the hollow ring, from within the hollow ring, biasing the inner wall toward a pipe that is inserted through the seal. This presses the oblique tapered annular ribs against the pipe.
As the oblique ribs diverge, it could be difficult to insert the pipe from either end of the seal. In order to ease entry of the pipe into the seal, the operator accesses the ends of the spring via the axial passageway in the concrete, and squeezes the ends of the spring to release the constricting force of the spring on the inner wall.
U.S. Pat. No. 3,813,107, patented May 28, 1974, by J. Ditcher, describes a hollow walled ring of flexible elastomeric material, the ring having the general configuration of a capital A in cross section, but with slightly splayed legs.
The ring is cast into the concrete wall peripheral to the opening through the wall to a depth in which the wall encloses the legs and is level with the top of the cross bar of the A shape. The apex of the A that remains above the concrete yields to the pipe, forming a hollow, slightly splayed over, oval seal against the pipe as the pipe is pushed through the seal.
U.S. Pat. No. 4,103,901, patented Aug. 1, 1978, by J. Ditcher, describes an assembly which is described here as seen in cross section, in order, from the periphery toward the center of an annulus of flexible elastomeric material. It is a radially oriented T with a bulbous bottom end, followed by a first oblique leg extending beyond one side of center line, followed by a reverse angled second oblique leg which crosses back to the other side of center line, ending in a bulbous termination. The bulbous termination is an O-ring which grips the pipe that is inserted through the seal. The T with bulbous bottom end is fully embedded in the concrete. Because the O-ring has little latitude for expansion and may resist insertion of the pipe, a temporary lubricated nose cone of frustoconical shape is sometimes placed on the pipe before it is inserted through the O-ring. If the pipe is smaller than the O-ring, a stainless steel tension band may be placed over the second oblique leg to clamp it around the pipe.
U.S. Pat. No. 4,350,351, patented Sep. 21, 1982, by A. E. Martin, describes an assembly which is described here in cross section, taken in order, from the periphery toward the center of an annulus of flexible elastomeric material. It is a first bead, a second bead of the same diameter as the first bead, a short radial leg about the same length as the bead diameter. The first and second beads, and about one half of the short leg are embedded in the concrete. An oblique leg about three and one half times the length of the short radial leg is attached to the short leg. The oblique leg is directed about 60 degrees from the radial away from the pipe receiving opening of the seal. The end of the oblique leg has an integral bead with a reverse curl toward the back of the leg. The reverse curl holds a hollow core ring that is preferably glued to the reverse curl.
When the pipe is pushed into the seal it contacts the front of the oblique leg, the oblique leg is forced outward whereby the leg becomes parallel to and in intimate contact over its full length with the outer wall of the pipe, and the hollow core ring becomes sandwiched between the reverse curl and the inner wall of the opening through the concrete. The sandwiched ring increases pressure of the leg against the pipe to make a firmer seal on the pipe.
U.S. Pat. No. 4,333,662, patented Jun. 8, 1982 by W. D. Jones, describes an annulus of flexible elastomeric material which is described here as seen in cross section, taken in the direction from a hollow ring in sealing contact with the pipe, toward the outer radial periphery of the seal assembly. It is the hollow ring a short radial connector leg attached to a pyramidal base with surfaces that diverge at a dihedral angle of about 140 degrees relative to one another. The diverging elastomeric surfaces protect the pipe from being damaged by the concrete surface of the opening. The lower portion of the base is cast into the concrete which forms the opening through the wall. Additional legs extend, one from each side of the base, and cover the remaining concrete on the inward facing surface of the opening through the wall. Each leg then folds back inward in a V, where the outer leg of the V is also cast in the concrete.
U.S. Pat. No. 4,342,462, patented Aug. 3, 1982 by J. Carlesimo, describes an annulus of flexible elastomeric material which is an outer cylindrical housing that fits within the opening of the concrete housing and has a radially outward extending element embedded in the concrete. A first cylindrical wall having a diameter that is smaller than the diameter of the cylindrical housing and having a first end and a second end is attached by the first end to one end of the housing and extends axially beyond the housing. A second cylindrical wall having a diameter that is smaller than the diameter of the first cylindrical wall is attached to the second end and extends axially away from the cylindrical housing. A strap around the second wall clamps the second wall around pipe that extends through the housing.
U.S. Pat. No. 5,286,040, patented Feb. 15, 1994 by N. W. Gavin, describes an annulus of flexible elastomeric material comprising an outer cylindrical wall that fits within the opening in the concrete housing and has a radially outward extending element embedded in the concrete during the casting of the concrete housing. The outer tubular wall further has an inward depending, frustoconical wall. The smaller diameter end of the frustoconical wall seals against the pipe. A diaphragm attached to the annular edge of the smaller diameter end and sealing over the smaller diameter end has different diameter tear out rings so that various size openings can be made at the smaller diameter end to seal around various diameter pipes. In casting the seal in the concrete wall of the housing, the seal is mounted by the frustoconical wall of the seal, on a frustoconical plug which is mounted on a movable portion of the wall of the mold. Axially extending pins on the diaphragm engage the smaller diameter face of the frustoconical plug and align the seal about the axis of the cylindrical wall in a preferred rotational position. U.S. Pat. No. 4,951,914, patented Aug. 28, 1990 by Meyers et al., describes an annulus of flexible elastomeric material comprising an outer cylindrical wall that fits within an opening in a wall of a concrete housing and has a radially outward extending element embedded in the concrete during the casting of the concrete wall of the housing. The outer cylindrical wall has an inward depending, frustoconical wiper attached by the larger diameter end to one end of the cylindrical wall. The smaller diameter end of the frustoconical wiper extends into the cylinder and seals against the pipe.
In casting the seal in the wall, a frustoconical plastic mandrel bolted on a swing out portion of the mold wall seats in the frustoconical wiper of the seal. The mandrel has, at the radially outward edge of the smaller diameter end, a gripper portion which releasably frictionally retains the free end of the frustoconical wiper wall from one side during casting of the seal assembly in the concrete wall of the housing. An annular knock out plug or plate, rests against the smaller diameter end of the mandrel within the confines of the outer cylindrical wall ill order to prevent entry of liquid concrete into the space between the outer cylindrical wall and the frustoconical wiper.
Although prior art inventions may serve the purposes for which they were intended, there are still problems which must be solved if a full feature embedded in concrete septic tank seal for pipes is desired.
For example, an oblique sealing element may not line up with the ribs on some pipes. Space between a pair of oblique ribs varies with constrictive pressure on the pipe because of the oblique angles. Ribbed pipe may interfere with the full seating of each rib of a plurality of sealing ribs against the pipe. A seal element that splays over to one side or the other as the pipe is pushed through the seal may not follow into the minor diameter of the ribs of a ribbed pipe. A closely supported O-ring seal may not follow completely, or yield sufficiently, to the contour of a corrugated pipe as it is thrust through the seal. An auxiliary clamp or spring which must be adjusted may add unacceptable inconvenience or cost to installation of the pipe in the subterranean concrete vessel on the job site.